1. Field of the Invention
The invention relates to channel classification, and more particularly, to methods and transceivers of channel classification using curves which have some relationship of ratios obtained by the hierarchical constellation, applied in orthogonal frequency division multiplexing (OFDM) systems.
2. Description of the Related Art
Recently, the application of the orthogonal frequency division multiplexing system has become one of the most important wireless communication technologies. Data can be easily and efficiently transmitted and received in the wireless communication environment because of the high transmission rate of the orthogonal frequency division multiplexing system. Therefore, the orthogonal frequency division multiplexing scheme is applied to, for example, Digital Audio Broadcasting (DAB), Digital Video Broadcasting-Terrestrial/Handheld (DVB-T/H), Wireless Fidelity (Wi-Fi) and Worldwide Interoperability for Microwave Access (WiMAX) etc., and the orthogonal frequency division multiplexing scheme has recently been regarded as a 4th-Generation Wireless System.
When the data transmitted by the orthogonal frequency division multiplexing scheme passes through the channel, the transmitted data will become distorted because of the channel effects. Therefore, the received data and the transmitted data are different. In order to solve this problem, the received data must be processed in the receiver such as in channel estimation and channel compensation etc. The channel effect must be estimated, which is regarded as channel estimation. The data affected by channel effect can be restored accurately to decrease the signaling distortion affected by channel effect such that the performance of orthogonal frequency-division multiplexing (OFDM) system becomes better and the bit error rate can be reduced. Therefore, determining how to classify channels is the most important challenge facing the development of the orthogonal frequency division multiplexing systems.